* If it has a standard open differential: Use a conventional 75W-140 gear oil. Some synthetic blends are also suitable, but check your owner's manual.
* If it has a limited-slip differential (LSD): You must use a gear oil specifically formulated for limited-slip differentials. These often contain friction modifiers to prevent chattering and premature wear. Look for an oil that explicitly states it's compatible with limited-slip differentials. The viscosity will likely still be 75W-140, but check your owner's manual.
Before you buy anything:
1. Consult your owner's manual: This is the most crucial step. It will specify the correct type and viscosity of gear oil for your Expedition's rear differential.
2. Check the differential tag: There might be a tag on the differential itself (usually on the top or side) providing information about the type of differential and recommended oil.
3. Consider the climate: If you live in an area with extreme temperatures, you might consider a synthetic gear oil for better performance in both hot and cold conditions.
Failing to use the correct oil can damage your rear differential, leading to expensive repairs. It's better to be certain before you change the oil.
